f(x)=m·n=√3sin2x+2-2cos²x
=√3sin2x-cos2x+1
=2sin(2x-π/6)+1,
f(x)的增区间为[-π/6+kπ,π/3+kπ],k∈Z；
f(x)的减区间为[π/3+kπ,5π/6+kπ],k∈Z.